Conventional components used to produce diffused light have included diffusive glass, which has been employed in a number of applications in the display industry. These applications include bezel-free television systems, liquid crystal displays (LCDs), electrophoretic displays (EPD), organic light emitting diode displays (OLEDs), plasma display panels (PDPs), micro-electromechanical structures (MEMS) displays, electronic reader (e-reader) devices, and others.
It has been discovered, however, that commercially available diffusive glasses do not meet certain new and important requirements for the emerging display industry.
The desire for the compounding effects of thinner, lighter and more energy efficient displays has led to the development of so-called transflective displays. Transflective displays are for the most part translucent (semi-transparent), and are being commercially implemented in several venues. Notable applications of transflective displays (which may also be referred to herein as translucent displays) include vending machine doors, freezer doors, retail advertising, augmented reality screens, heads-up displays in the automotive industry, smart windows for offices, portable consumer electronics, and security monitoring.
Translucent displays, however, are susceptible to some poor performance characteristics. Conventional translucent displays incorporate both a transmissive medium and a reflective medium giving the display the versatility of being used both indoors and outdoors. The resulting “transflective medium” may include openings-on-metal, a half-mirror metal sheet, a multilayer dielectric film, orthogonal polarization transflectors, etc. Independent of the implementation, however, these so-called transflective displays suffer from a number of shortcomings. Indeed, since such displays only partially transmit and reflect light, the contrast ratio of the display is greatly limited. For example, commercially available translucent displays offer only about 15% transmission, and the performance is even lower in reflection. In an indoor setting, conventional transflective displays not only suffer from low illumination, but the reflective component reflects too much of the ambient scenery and ultimately distorts the principal information to be displayed. Additionally, color rendering is challenging since the image is mixed with the natural transparent color of the display.
For most practical applications, a translucent display requires the support of backplane illumination (via a transparent backlight element). In order to maintain translucency, the backlight needs to be fully transparent in an OFF-state and fully illuminated in an ON-state. Additionally, the use of a transparent backlight supersedes the use of the conventional reflective medium, and therefore by eliminating the reflective medium, both image brightness and image quality can be vastly improved.
It has been discovered, however, that existing technology for providing sources of backplane illumination, are not satisfactory in meeting certain cost and performance requirements of the marketplace.